This research has the following components: 1. Correlation of Body Surface Potential Maps (based on potential recorded at 180 electrode sites on the torso) with cardiac physiology and patholody in pediatric patients using non-ECG diagnostic data (derived from catheterization measurements as well as other measurements which are non-invasive) and also using ECG and VCG recordings. 2. Studies and development of new methods for improved generation and display of maps. Use of pattern recognition for classification and for identification of intervals. Development of pseudo-color techniques. 3. A study of the inverse problem leading to improved epicardial maps derived from body surface potential maps. The epicardial map has been shown to be normalized (independent of body shape and discontinuity of conductivity) and furthermore displays regional information with better fidelity than surface maps. 4. Improvements in the technology of acquiring maps to make it simpler and with improved signal/noise. Improvements on the inflatable vest design and the use of dry active electrodes.